However, no data is yet available about safety and tolerability of chitosan-N-acetylcysteine in subjects wearing contact lenses. This is of special interest because the tear film is critical to successful contact lens wear. Disturbances of the quantity or quality of the tear film results in intolerance of contact lens wear and possible damage to the ocular surface. This trial seeks to investigate the local tolerability and possible ocular discomfort of chitosan-N-acetylcysteine eye drops after repeated instillation .